Aggregate of pressure cylinders

ABSTRACT

An aggregate ( 10′ ) of pressure medium cylinders ( 11′, 12′ ) are used especially where there is required a relatively large length of stroke. At least a first ( 11′ ) and at least a second ( 12′ ) pressure medium cylinder are arranged by the side of each other with their longitudinal axes ( 11   a,    11   b ) extending mutually parallel. The cylinder parts ( 13′, 14′ ) of the cylinders are rigidly connected to each other at least in pairs. Piston rods ( 17′, 18′ ) of said first and second cylinders are turned respectively in pairs in mutually opposite axial directions.

The present invention relates to an aggregate of pressure mediumcylinders, especially for use where a relative large length of stroke isrequired. More specifically the invention comprises an aggregate ofpressure medium cylinders where the piston rod of a first cylinder isdirected away from the piston rod of a second cylinder where thecylinder portions of the cylinders are rigidly connected to each otherand where the longitudinal axes of the cylinders run parallel to thelongitudinal axis of the aggregate.

By the term “medium” is meant preferably a gaseous or liquid fluid whichis employed to drive the cylinders in the aggregate. On pressure settingeach cylinder chamber with a gaseous or liquid fluid, the respectivepiston rod is pushed out, and reversely, on venting off the fluid fromthe cylinder chamber, the piston rod is drawn into the cylinder.

A usual problem with pressure medium cylinders, which have a relativelylarge length of stroke, is that they become unstable during use and areapt to break at the transition from cylinder to piston rod.

Attempts have been made to remedy this drawback by employing anaggregate of pressure medium cylinders in the form of a number of doubleacting telescopic cylinders, that is to say a number of cylinders whichare arranged along a common central axis. However such an aggregate hasa weakness having relatively thin piston rods in the final telescopiclink and a corresponding danger of breaking at the transition fromcylinder to piston rod in said final telescopic link.

In U.S. Pat. No. 4,733,598 a telescopic arrangement is referred to whichcomprises a simple aggregate of three telescopic pipes together withonly two oppositely directed pressure medium cylinders. The cylindersare disposed side-by-side, that is to say roughly on each side of thecentral axis of the telescopic arrangement. The cylinders are secured toa telescopic pipe radially most central, while the respective piston rodhas the outer end secured to a telescopic pipe radially outermost orradially innermost. The two cylinders are disposed side-by-side on eachside of the central axis of the telescopic arrangement. The constructionnecessarily provides an oblique load between the outer ends of thepiston rods in a direction which extends obliquely of the central axisof the aggregate/telescopic arrangement. The surrounding telescopicpipes are correspondingly obliquely loaded by the pressure mediumcylinders, especially in the fully pushed out condition of the pistonrods.

In U.S. Pat. No. 3,250,182 there is referred to according to FIGS. 1-7 asimple cylinder aggregate of a kind equivalent to that described in theafore-mentioned U.S. Pat. No. 4,733,598. In FIGS. 8-9 an arrangement isshown of a still simpler kind, without telescopic pipes and without amechanical connection between the pressure medium cylinders, that is tosay for completely different purposes than according to the invention.

With the present invention the aim is an aggregate having a robust andoperatively reliable construction practically, where inter alia thedanger of breakage of piston rods during use is reduced.

The aggregate according to the invention is characterised in that anumber of cylinders of a first type and a number of cylinders of asecond type are arranged in an annular group about the longitudinal axisof the aggregate, the cylinders of the first type being received inintermediate spaces between cylinders of the second type, while thepiston rods of the first type of cylinders are rigidly connected to eachother at associated outer ends, and the piston rods of the second typeof cylinder are mutually rigidly connected to each other at associatedouter ends.

By arranging pressure medium cylinders of a multi-cylindered cylinderaggregate according to the invention double stroke length and a multipleoutgoing power can generally be achieved, that is to say double outgoingpower in an aggregate of two cylinders and quadruple outgoing power infour cylinders, etc.

Consequently with a robust construction, but nevertheless a relativelyshort cylinder portion, there can be achieved a relatively large strokelength and simultaneously a relatively large outgoing power.

According to a first embodiment of the invention the aggregate isfurther characterised in that the cylinders of the first type areequipped with a first common power transmitting slide, and the cylindersof the second type are equipped with a second common power transmittingslide, the slides being arranged centrally between the cylinders andbeing slidable along a common central axis.

By means of the slides the accumulated outgoing power of the aggregatecan be conveyed along the common central axis and relieve in aneffective manner flexural stresses which otherwise would be able tooccur in the piston rods.

According to a second embodiment of the invention the aggregate isfurther characterised in that the cylinder portions of the cylinders aremade coherently of a common piece of material.

According to a third embodiment of the invention the aggregate isfurther characterised in that the piston rods of the first cylinders areat respective outer ends mutually rigidly connected to each other viatheir respective first local fastening points in a first plane, and thatthe piston rods of the second cylinders are at the outer end mutuallyrigidly connected to each other via their respective second localfastening point in a second plane which crosses the first plane.

By means of the annular arrangement of cylinders the total outgoingpower can be readily localised along a common central axis, one beingable to ensure with a mutually rigid connection between the piston rodsat each of the ends of the aggregate that the total out going power ofthe aggregate can be conveyed along the common central axis. In additionflexural stresses, which could otherwise occur in the piston rods, canbe relieved in an effective manner.

Consequently in the invention a larger number of pressure mediumcylinders is employed than that which is known previously. With the newsolution pressure medium cylinders which have the same piston outwarddisplacement direction, can be placed in pairs, diametrically above eachother on their respective sides of the central axis of the aggregate.

According to the invention the oblique loads which arise according tothe US publications can be avoided. Consequently according to theinvention the possibility is achieved for a more reliable mode ofoperation and the possibility for transmitting significantly greaterpushing forces than those which are possible according to the USpublications. According to the invention it is consequently a questionof a new solution and a considerable advance in the field.

Further features of the present invention will be evident from thefollowing description having regard to the accompanying drawings, inwhich:

FIG. 1 shows an aggregate, as known per se, comprising a pair ofmutually parallel pressure medium cylinders with mutually oppositelydirected piston rods.

FIGS. 1a and 1 b shows the aggregate according to FIG. 1 illustrated inend view, seen from two opposite ends.

FIG. 2 shows in a first embodiment a modified design of the aggregateaccording to FIG. 1, constructed as according to the invention. For thesake of clarity the drawing shows only the one of a first pair ofdiametrically opposite cylinders and the one of a second pair ofequivalent diametrically opposite cylinders. Besides FIG. 2 shows thecylinder aggregate turned 90° relative to the position illustrated inFIG. 3.

FIGS. 2a and 2 b show the aggregate according to FIG. 2 illustrated inend view, seen from two opposite ends. For the sake of clarity only theone half of the aggregate is illustrated.

FIG. 3 shows in a second embodiment an aggregate according to theinvention of two pairs of mutually parallel pressure medium cylinderswhose piston rods are arranged in pairs in opposite directions.

FIGS. 3a and 3 b show end views of the aggregate according to FIG. 3,seen from opposite ends.

FIG. 4 shows schematically in perspective a modified design of theembodiment according to FIG. 3 with the cylinders made in a coherentconstruction of one and the same piece of material.

In FIG. 1 there is shown an aggregate 10 of two pressure mediumcylinders 11,12 mutually secured together, as known per se, and withmutually parallel longitudinal axes 11 a, 12 a. The cylinders 11,12 areillustrated having mutually like designs.

The cylinders 11,12 have cylinder parts 13 and 14, which endwise areuniformly terminated and which are rigidly connected to each other viacommon fastening brackets 15 and 16, The cylinder parts 13,14 form,together with fastening brackets 15,16, a rigid and robust cylinderaggregate having effective bracing and shoring up between the cylinderparts 13,14.

In other words with cylinders 11,12, which are arranged by the side ofeach other, instead of after each other, the length dimension of theaggregate can be reduced and the construction of the aggregate therebycompressed by increasing the lateral dimension at the expense of thelength dimension. Consequently the cylinder parts 13,14 will be able tobrace each other mutually at the same time as the working volume of thecylinder parts 13,14 can be utilised in an economic manner.

The cylinders 11,12 are equipped with piston rods 17 and 18, whichproject endwise outwards in mutually opposite directions. In that thepiston rods 17,18 project outwards in opposite directions each from itsseparate cylinder part 13,14 an effect is obtained, which not onlycorresponds to conventional double acting cylinders, but which yieldsdouble outgoing power. This is achieved in addition to the accumulatedcompressed length dimension of the aggregate.

In many cases of use, one can prevent, for example by pivotallyconnecting outer ends of the piston rods at associated fastening points,as a consequence of the mutual bracing between the cylinder parts, theoccurrence during use of breakage of the piston rods at the transitionsbetween piston rod and cylinder part.

In order to further reinforce the aggregate and counteract the tendencyfor breakage of the piston rods there can be arranged, as is shown inthe alternative embodiment according to FIG. 2, extra support and/orbracing arrangements in connection with the solution which is shown inFIG. 1.

In FIG. 2 there is illustrated a first, transversely extending supportmember 20 a or 20 b, which on the one side is rigidly connected to theouter end of the piston rod 17 or 18 and on the other side is rigidlyconnected to a rod-shaped slide 21 or 22. The slides 21,22 are with theone end 21 a fixedly connected with a first local fastening point 23,and with the one end 21 b fixed connected with a second local fasteningpoint 24. The slides 21,22 are arranged in the illustrated embodimenttelescopically displaceable along a common central middle axis 25, whichcan be arranged centrally between the cylinders, if desired centrallythrough the aggregate.

Alternatively the one slide 21, in the form of a simple slide bar,passes centrally between the cylinder parts 11,12, as is shown in FIG.2a, while the other slide 22, in the form of two parallel slide bars 22a, 22 b, can pass just by and each on its side of the slide 21, withmutual shoring up between the slides 21,22 and possibly with extrashoring up of the cylinder parts 11,12, as is shown in FIG. 2b.

As illustrated in FIGS. 2a and 2 b the piston rods are separatelysecured via other, obliquely extending support parts to the respectivefastening point 23 or 24.

In FIG. 3 there is illustrated an aggregate of four cylinders, that isto say two pairs of cylinders 11′,11′ and 12′,12′, arranged in anannular aggregate 10′ and fastened together with common end pieces 15′and 16′.

More specifically there is illustrated a first pair of cylinders 11′,11′which are arranged directly above each other at a certain mutual spacingand which have the piston rods 17′ directed axially outwards in the oneaxial direction. A second pair of cylinders 12′, which are arrangedcorrespondingly mutually directly above each other at a certain spacing,have the piston rods 18′ directed in a direction axially opposite to thepiston rods 17′. The cylinders 121 are arranged each on its side of thecylinders 11′ to form said annular cylinder aggregate.

It is evident from FIG. 3b that piston rods 17′ of the first cylinders11′ extend mutually parallel in a first plane, for example as shown in avertical plane, while it is evident from FIG. 3a that the piston rods18′ of the second cylinders 12′ extend mutually parallel in a secondplane, for example as shown in a horizontal plane. The piston rods 17′can consequently be braced in the first plane, in the one end betweenfastening points (not shown) on the piston rods and the other end inassociated cylinder 11′. The piston rods 18′ can be bracedcorrespondingly in the second plane at the one end between localfastening points and at the other end in associated cylinder part 12′.Consequently the second plane crosses the first plane. The cylinderparts 11′,12′, which are arranged in an annular arrangement, constitutefor their part an effective junction for the bracing of both pairs ofpiston rods 17′,18′ in different planes between opposite ends of thecylinder aggregate 10.

As shown in FIGS. 3, 3 a, and 3 b, it is possible to equip the cylinderaggregate with additional cylinders, indicated at 17″ and 18″, forexample with the cylinders arranged in a single ring or in two or moreconcentric rings. Alternatively, two or more cylinder aggregates can bearranged in a row.

In a favourable constructional design, as shown schematically in FIG. 4two pairs of cylinders 11″ and 12″ can be fashioned in a common piece ofmaterial, for example in a common block-shaped construction 30, byboring out cylindrically hollow spaces 31,32 individually from mutuallyopposite ends of the piece of material. There can be obtained hereby aconstruction which is simple as to manufacture and use, but at the sametime robust and concentrated.

What is claimed is:
 1. An aggregate of pressure medium cylinders,comprising: a plurality of first-type cylinders, each first-typecylinder having a first-type cylinder portion with a longitudinal axisand a first-type piston with an outer end, wherein the first-type pistonis in displaceable relation with the first-type cylinder portion alongthe longitudinal axis and the outer ends of the first-type pistons aredisposed in the same direction and rigidly connected to each other; aplurality of second-type cylinders, each second-type cylinder having asecond-type cylinder portion with a longitudinal axis and a second-typepiston rod having an outer end, wherein the second-type piston rod is indisplaceable relation with the second-type cylinder portion along thelongitudinal axis and the outer ends of the second-type pistons aredisposed in the same direction and rigidly connected to each other; andfirst and second common power-transmitting slides centrally arrangedbetween the first-type and second-type cylinders and movable along acommon axis, wherein the first-type and second-type cylinders arearranged in an alternating annular formation about an aggregate axis,the first-type and second-type cylinders portions are rigidly connectedto each other in a longitudinally parallel manner, the outer ends of thefirst-type and second-type pistons are oppositely directed, thefirst-type pistons are connected to the first common power-transmittingslide, and the second-type pistons are connected to the second commonpower-transmitting slide.
 2. The aggregate of claim 1, wherein thefirst-type and second-type cylinder portions are formed from a commonpiece of material.
 3. The aggregate of claim 1, wherein the longitudinalaxes of the first-type cylinder portions form a first plane, thelongitudinal axes of the second-type cylinder portions form a secondplane, and the first and second planes intersect each other.
 4. Theaggregate of claim 1, wherein the outer ends of the first-type pistonsare located in a first plane.
 5. The aggregate of claim 4, wherein thefirst plane is perpendicular to the longitudinal axis of the first-typecylinder portion.
 6. The aggregate of claim 5, wherein the outer ends ofthe second-type pistons are located in a second plane.
 7. The aggregateof claim 6, wherein the second plane is perpendicular to thelongitudinal axis of the second-type cylinder portion.
 8. The aggregateof claim 1, further comprising additional cylinders arranged an annularformation circumscribing the annular arrangement of the first-type andsecond-type cylinders.
 9. The aggregate of claim 8, wherein the annularformation of the additional cylinders and the annular arrangement of thefirst-type and second-type cylinders are concentric.
 10. An aggregate ofpressure medium cylinders, comprising: a plurality of first-typecylinders, each first-type cylinder having a first-type cylinder portionwith a longitudinal axis and a first-type piston with an outer end,wherein the first-type piston is in displaceable relation with thefirst-type cylinder portion along the longitudinal axis of thefirst-type cylinder portion and the outer ends of the first-type pistonsare disposed in the same direction and rigidly connected to each other;a plurality of second-type cylinders, each second-type cylinder having asecond-type cylinder portion with a longitudinal axis and a second-typepiston rod having an outer end, wherein the second-type piston rod is indisplaceable relation with the second-type cylinder portion along thelongitudinal axis of the second-type cylinder portion and the outer endsof the second-type pistons are disposed in the same direction andrigidly connected to each other; and first and second commonpower-transmitting slides centrally arranged between the first-type andsecond-type cylinders and movable along a common axis, wherein thefirst-type and second-type cylinders are arranged in an alternatingformation, the first-type and second-type cylinders portions are rigidlyconnected to each other in a longitudinally parallel manner, the outerends of the first-type and second-type pistons are oppositely directed,the first-type pistons are connected to the first commonpower-transmitting slide, the second-type pistons are connected to thesecond common power-transmitting slide, the longitudinal axes of thefirst-type cylinder portions form a first plane, the longitudinal axesof the second-type cylinder portions form a second plane, and the firstand second planes intersect each other.
 11. The aggregate of claim 10,wherein the first-type and second-type cylinder portions are formed froma common piece of material.
 12. An aggregate of pressure mediumcylinders, comprising: a block fashioned from a common piece of materialhaving first and second opposing surfaces; a plurality of first-typepistons, each first-type piston with an outer end and located in afirst-type bore terminating at an opening of the first surface, whereinthe first-type piston is displaceable along an longitudinal axis of thefirst-type bore, and the outer ends of the first-type pistons arerigidly connected to each other; a plurality of second-type pistons,each second-type piston with an outer end and located in a second-typebore terminating at an opening of the second surface, wherein thesecond-type piston is displaceable along an longitudinal axis of thesecond-type bore, and the outer ends of the second-type pistons arerigidly connected to each other; and first and second commonpower-transmitting slides centrally arranged between the first-type andsecond-type cylinders and movable along a common axis, wherein thefirst-type and second-type bores are arranged in an annual formationabout an aggregate axis, the longitude axes of the first-type andsecond-type bores are parallel to the aggregate axis, the first-typepistons are connected to the first common power-transmitting slide, andthe second-type pistons are connected to the second commonpower-transmitting slide.